The present disclosure relates to an automatic step variable attenuator which is capable of being applied to a front-end portion in a receiver of either a radio communication device or a television (TV) system, and a radio communication device to which the automatic step variable attenuator is applied.
For the purpose of enabling an RF received signal having a wide range to be received, a radio receiver includes a variable gain function.
Normally, for enabling the range to be obtained as largely as possible, the variable function is not consolidated into one element, but is dispersed into plural elements in many cases.
The variable gain functional element is roughly classified into a variable gain amplifier and a variable attenuator depending on whether or not the variable gain functional element has a gain of one or more power.
In particular, the latter is normally high in linearity because it can be mainly composed of a passive element such as a resistive element or a switch. Thus, the latter is mounted to the front-end of the receiver, whereby a variable gain function is obtained without deteriorating a signal when an excessive RF received signal is inputted thereto.
For example, there is known a Low-IF type radio receiver including an element having three variable gain functions in a receiver signal path. In this case, an automatic step variable attenuator, a low-noise variable gain amplifier or an IF variable gain amplifier corresponds to the variable gain functional element.
An automatic gain controlling circuit in which the automatic step variable attenuator is mounted to the front-end portion of the receiver is known as this sort of technique. This sort of technique, for example, is disclosed in Japanese Patent Laid-Open No. 2000-286654.